Since Medicare was enacted in 1965, the program has excluded coverage for outpatient prescription medications except for injection drugs furnished by a physician. It is now widely recognized that the elderly face an erosion of prescription benefits as insurers respond to mounting fiscal pressures with a variety of cost-cutting and cost-shifting measures. Medicare beneficiaries must rely on a range of supplemental sources to help with drug expenses. The Medicare Current Beneficiary Survey (MCBS), administered annually to a representative national sample of elderly and disabled adults enrolled in Medicare, represents the gold standard for information on rates and sources of prescription coverage among elderly Americans. However the MCBS provides little information on cost-related non-compliance with medication regimens, and there are no other national data sources. While preliminary research documents the relationships among out-of-pocket medication costs, rates of non-compliance, and adverse clinical outcomes, no national study to date has addressed whether such cost-related barriers lead to under use of essential drugs for chronic illnesses, substitution of over-the-counter or alternative medicines, or reductions in physician visits. This project will establish a permanent, ongoing national data resource that permits policymakers and researchers to measure, monitor, and identify changes in cost-related under use of medications (CRUM) among elderly Medicare beneficiaries. We will develop new, comprehensive measures of CRUM; validate the measures in a survey of approximately 200 elderly enrollees in a large health plan; integrate the measures in the MCBS for annual surveys of approximately 15,000 non-institutionalized elderly Medicare enrollees (the cost of which will be borne by the US Department of Health and Human Services, Center for Medicare and Medicaid Services); and analyze MCBS data to identify the extent to which CRUM is associated with patient socio-demographics, health status and medical conditions, source of prescription coverage, and out-of-pocket prescription costs. [unreadable] [unreadable]